Hot Water when the calorifier goes cold?????????????

[RupertW]

It's not exactly so, because the lower power means the heater element will run cooler, so have a lower resistance than at 230V.
It might be wise to be getting the water hot enough to kill legionella?

Interesting on legionella - a lot of the time there will be pipe work anyway well below a killing temperature and a short use of engine (takes about half an hour to reach full temperature) will also leave it lower. Has any legionella issues ever come from a boat’s system?

 

[RupertW]

Four times the time actually. For a 230v element at 110v both the current and the volts are halved so watts are one quarter.

Doh. Of course and that’s better for battery use as well as I have perhaps 6 hours a day of wasted sunlight.

 

[AntarcticPilot]

Interesting on legionella - a lot of the time there will be pipe work anyway well below a killing temperature and a short use of engine (takes about half an hour to reach full temperature) will also leave it lower. Has any legionella issues ever come from a boat’s system?

The main concern would be in using a shower head, but I suppose most people wouldn't try and use a shower if the water wasn't hot enough. IT would be interesting to know if there are any statistics! Of course, I suppose most of us use other means of sterilizing the water in our tanks - I certainly use purification tablets on a regular basis.

 

[RupertW]

Interesting again - we mostly shower tepid or for me, almost no hot water at all as I shower to keep cool. That’s why only a little heating is needed.

 

[scottie]

We have a Moody Eclipse with a Volvo raw-water cooled engine fitted with a calorifier (and immersion heater for shore power); we get reasonably hot water after the engine has been running, but, inevitably, after a few hours the water isn't hot. Given that we have the luxury of a good size shower facility in the heads, I'd like to have a method of generating hot water on demand.

Our previous boat (Vancouver 32) had a gas heater in the heads, but these seem to have fallen out of favour, presumably for safety reasons; fitting one would probably be slightly awkward given the layout in the heads. I know that some people advocate using an inverter connected to the immersion heater, but I'm wondering about the drain on the batteries ( 2x 110ah for domestic use).

The thought occurred to me that using a small petrol generator wired into the immersion heater might be an answer, but I'm not sure what output would be needed or indeed how long it might need to run - I'm sure I'm not alone in being very irritated by boats running generators for hours in quite anchorages.


Any thoughts/experiences would be useful - thanks.

If you could still get one a fresh water conversion kit is your answer
The raw water thermostat is rated much lower than fresh so neither the engine nor calorifier gets very hot unfortunately just changing the stat is NOT advised as seawater should be cooler than fresh to avoid corrosion problems
Anything else is just mitigation

 

[SiteSurfer]

I’m surprised no one has mentioning the green 12v heater coils with the smart box of tricks which uses solar power to heat the water in the calorifier. Just seen a video on it and it seems like a good solution albeit pricey.

Any views?

 

[Mistroma]

I’m surprised no one has mentioning the green 12v heater coils with the smart box of tricks which uses solar power to heat the water in the calorifier. Just seen a video on it and it seems like a good solution albeit pricey.

Any views?

The calculation is simple enough (already explained by Arctic Pilot) and is really directly related to temperature difference, volume of water being heated and allow for losses (poor insulation etc.). The guy with 1.4kW solar won't have much of a problem re-heating a well insulated tank each day. Huge solar output and not always starting from cold anyway.

Solar showers or black killa-spray also work well enough. A cruder solution than the 12V heater coils but much cheaper.

My boat doesn't have direct raw water cooling and allows the water to get well above the set point on the electric element. Must be 85-90C as it seems to last for 2-3 days. Tank is well insulated, we avoid using hot water just for hand/face washing and tank has a cold water mixer valve. The mixer valve adds cold water to a safe temperature and allows safe use of very hot stored water.

 

[Deleted member 36384]

Can you not just run the engine 'on demand', say 30 minutes before a shower is required? I find my system heats up very quickly.

 

[Venus1]

If you could still get one a fresh water conversion kit is your answer

+1
A fresh water cooling conversion for the engine, if available, might be less complicated and more cost effective than other options. I believe raw water cooled engines run at ~ 64 degrees whereas fresh water cooled versions run at ~ 90 degrees. This, with good insulation of your tank, should allow showers the following day...

 

[RupertW]

Can you not just run the engine 'on demand', say 30 minutes before a shower is required? I find my system heats up very quickly.

It’s about trying to be self sufficient so using the engine is cheating. Until last year we needed to use the engine twice a day even in a marina as we only had a belt driven fridge but with a 12v fridge and some solar we know don’t need the engine or marina power for fridge, autohelm, device charging,lights or anything else - except water heating on the second day and subsequent daysat anchor.

It’s a nice little puzzle - 12v element no good as I don’t want to lose my 230v one when on mains power in a marina.

I think the neatest idea is black painted old domestic fridge coil on a board in the sun with a little 12v pump to circulate it in and out of the hot water tank. But the simplest one is using excess solar power and invertor if lots of spare solar.

 

[grumpy_o_g]

Slight thread drift here but.... given the huge amount of energy required to heat water.....if I drink a couple of litres of ice cold water per day will I be able to eat more Frey bentos pies without weight gain?

Yes, body uses far more calories when it's cold. Rations difference between tropics and arctic is as much as 2,000 calories per day for Marines.

 

[grumpy_o_g]

I beg to differ - we make 40l every day of scalding hot water using a 2Kw inverter - we do have 1400w of solar and wait until lunch time when the batteries are full and then we can run it effectively for hours if need be just from the solar input without training the batteries at all - they stay on float charge mode the whole time ... Without solar just doing it from battery reserve would be a bad idea of course

The calcs are spot on but it's probably not a valid assumption that you're heating the water from cold. Even poor insulation will help keep some residual heat in the calorifier.

 

[No Regrets]

Despite having a 2Kw inverter and a pair of 50A/h Alternators and 720 A/h battery bank as well as a calorifier (Hot water one way or another!) I get SWMBO to shower while we are motoring, so whenever we moor up, we have a full tank of lovely hot water! Even leaving one engine running as soon as we stop will reheat the water if I want a shower.

Worth a thought!?

 

[John the kiwi]

My solution on a boat with no hot water is a 12volt camping shower (~20quid) and a 15 litre bucket.
One full kettle of boiling water into bucket, then made up with cold to desired shower temp.
I have taken the shower unit on flotilla as well, and we ended up using it most days as we like to shower in the morning by which time the calorifier was cold.
My unit came with a long cable to plug into lighter socket and easily reached the heads compartment.

Very cheap and suprisingly effective solution.

 

[noelex]

We use a different boat shower system that may be worth considering in your case. The system is better, at least for our needs, than traditional boat calorifier.

Our shower has a large sink that simply acts as a hot water container. This has a dedicated 24v pump that draws water from the sink sending it to a conventional shower rose.

The technique is to pour hot water into the sink then add some cold until the shower water is exactly the desired temperature and use the inbuilt pump to shower with this water. It is a showering method that we have used for many years and it works very well on a boat. The water temperature is perfect without fiddling with tap settings otherwise it is exactly like a normal shower to use.

One of the benefits is the versatility. The water can be heated from any source or mixture of sources such as solar (a black container on deck), the Reflex diesel heater or the propane stove. In summer we have enough solar that the shower water is heated on an electric kettle. Alternatively, if we are running the engine, the alternator will power the electric kettle. In winter we keep a kettle on the Reflex heater. The temperature can be mixed so it is exactly correct and you can shower anytime even if the engine has not been run for several days. I am fussy about shower water temperature. Lukewarm showers in cold climates. Yuk. It is also possible to shower with different water from that stored in the main tank, which can be useful if there is ready supply of water of questionable quality.

This is photo of our shower. There are two shower roses, one conventional, and one that works as described above. The seat lifts to reveal 3 large sinks or laundry tubs. Two are conventional sinks mainly used for clothes washing. The third can be also be used as sink but its primary purpose is to hold the hot water for the shower system.
Photo credit: Arthur Smeets

Edit: I see John the Kiwi has recomended a similar shower. Our system is basically a “built in” version of the system he is using. The shower pump, shower rose and “bucket” to hold the hot water in our case are all installed. The portable system John has described is a good way to see if you like the system.